In pH-stat feeding, the automatic pH control system of the batchoperation was switched off. The limiting substrate (see below) wasfed when the pH rose to above 7.0 indicating a depletion of the sub-strate. For each feeding, 60 mL of the culture broth was pumped outof the bioreactor and replaced with a mixture of 50 mL of double-strength fresh production medium and 10 mL of palm oil so thatthe final volume of the broth in the bioreactor was 1 L.